My favourite thing: the browser. The browsing is almost as good as on a desktop browser. The only missing feature is a Flash player.
My least favourite thing: I only get two to three days out of the battery. I am sure RIM will improve this with newer firmware releases.

I agree that the browser is indeed a massive improvement. It is now thus, comparable to iPhone browser in many ways, or the Nintendo Wii Opera browser, in that the BlackBerry Bold browser uses an incrementally zoomable view...

While not as good as the iPhone browser, it is much better. RIM needs to work on improving AJAX support so more Web 2.0 applications work properly -- For example, the iPhone can render maps.google.com to things like GMAIL (full web version), while the Bold doesn't yet... Of course, there's native apps, but these are good tests of AJAX (Web 2.0 capabilities), such as pannable maps, interactive features such as "Edit Post" in vBulletin without reloading the page, etc.

The rendering could be made a little faster, as the iPhone still has the edge here (both Bold and iPhone has similiar CPU speeds).

Zooming is not bad -- it is nicely antialiased -- I would like to see animated smooth zooming motions (ala Opera Mini or iPhone) that can be turned on/off, since that helps provide context, or a shortcut that allows me to quickly and smoothly zoom in/out, such as holding a key while spinning trackball. i.e. I'd like some kind of a quickie substitute for the iPhone "pinch zoom" motion. People who appreciate both the benefit of a BlackBerry and iPhone (without being polarized one way or another), would understand what I'm talking about...

Perhaps this is already included in an updated browswer, but that wasn't seen in the Bold Browser I tried out... That said, the browser is fun to use, definitely preferable over Opera Mini, and I've already made a post about keypress shortcuts that I've discovered in the browser!